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Monday, October 3, 2016

Q. Is it worth isolating my speakers and other equipment?

By Hugh Robjohns

With
properly designed and constructed monitors, whether active or passive,
you needn't worry about internal vibrations damaging electrical
components.

I would like to know how much benefit can be gained by isolating my
speakers and other gear from their supports — so-called 'seismic
isolation'. I recently saw a forum posting suggesting that passive
monitors have an advantage over active ones as, in the case of the
latter, vibrations from the speaker can affect the components of the
built-in amp. The benefits of decoupling equipment using springs that
have a very low resonance frequency so that it 'floats' was also
discussed. Apparently many things can benefit from this technique — not
just speakers but CD players and studio gear also. Improvements to the
stereo field and depth are said to be quite noticeable. I would like to
know if the £1300 I spent on an active Blue Sky System One (which I like
very much) would have been better spent on passive speakers and an
external amplifier. Can you shed any light on all of this for me please?

SOS Forum Post

Technical Editor Hugh Robjohns replies: With regards
to what you read about internal vibrations in monitors, in general
neither the active or passive form has an advantage in this regard, and
both potentially suffer exactly the same problem.

Clearly, there is a lot of sound energy inside most loudspeaker
cabinets, and if that energy is allowed to impact on electronic circuit
boards it is possible that some components might resonate and vibrate,
eventually resulting in damage to the solder joints or the components
themselves, and possibly such mechanical resonances might affect the
electrical signal passing through the components. However, this would
apply equally to passive crossover boards as much as active amplifiers.

In 30-odd years of playing around with loudspeakers in many and
various forms, I can't say I have ever found this to be a real problem. I
have occasionally come across speakers that have suffered component or
solder joint failures, but in all cases the causes have been traced to
faulty production or failures in quality control. When the faults were
fixed properly, none recurred as far as I am aware — even though you
would expect them to if the sole cause was sound vibrations within the
cabinet. So I am confident that this argument can be set aside as a
popular but completely unfounded myth.

Mechanical isolation of speakers or other devices from their supports
can be used to advantage in certain situations, but it is a complex
subject and it is easy for the inexperienced to make the situation worse
with inappropriate decoupling systems. In my experience, most equipment
works best when mounted on solid, heavy supports — there is nothing as
effective at controlling vibrations as a lot of mass.
However, sometimes it is necessary to come up with some form of
decoupling to prevent vibrations generated in one source from entering
an adjacent surface. The classic example is that of placing nearfield
speakers on a desktop, when the inherent speaker cabinet vibrations will
often cause the desktop to vibrate and resonate, resulting in unwanted
rattles. In this situation, placing the speakers on some form of
decoupling medium can improve matters — something like the Auralex
Mo-Pads, for example, are very effective. However, far better results
can be obtained by removing the speakers away from the table top
completely and mounting them properly on solid, heavy stands placed
directly on the floor.

Auralex Mopads can be used to isolate monitors placed on a desktop, but heavy-duty floor stands are best of all.

As far as equipment is concerned, I don't subscribe to the view that
properly designed and manufactured amplifiers and other electronics
should be decoupled to improve stereo imaging or anything else. However,
when it comes to systems involving some mechanical element — like
record players, CD players and so forth — unwanted vibrations entering
the mechanical system certainly can cause problems.

Most people are very well aware of the susceptibility of record
players to external mechanical or acoustic vibration. The required
tracking precision in CD players and DVD players is many orders higher,
and mechanical vibrations that reach the mechanism will affect the
accuracy of the tracking. Potentially, this will cause the tracking and
focus servos to work harder, forcing greater current flows at higher
frequencies through the motors. In cheaper designs, this may well affect
the power supply's stability and result in noise currents reaching
other parts of the circuitry. Reduced tracking precision can also
potentially result in a greater uncorrected error rate and far more
jitter. Cheap and poorly designed players are likely to suffer these
effects to a much higher degree than properly engineered equipment,
which will usually incorporate properly decoupled drives, effective
de-jittering circuitry, and so on.

It's a familiar scenario in the hi-fi world — people discover that
badly engineered equipment reacts 'unexpectedly' to different cables,
mechanical decoupling, or painting with a green pen — all of which
bestow a 'miraculous' benefit to the sound... and then declare (from no
scientific basis whatever) that all vaguely similar equipment will
behave the same. It's just not the case.

As to whether you would have been better off buying passive monitors
and an amp, the answer is probably not. I can think of some excellent
passive monitor and amp combinations for the rough cost you mention, and
in direct comparisons I dare say some people would prefer a passive
speaker and amp configuration over your Blue Sky System One. But it
comes down to personal preferences regarding sound, convenience and
styling, and how the system works in a given room. I think you can
continue to enjoy your Blue Sky system and completely disregard any faux concerns raised by the technical myth-spreaders!